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Item Thermodynamics of Liquid Mixtures of Methane and Ethene(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (09), 1977) Calado, Jorge C. G.; Soares, VirgIlio A. M.The total vapour pressure of liquid mixtures of methane and ethene has been measured as a function of composition at 103.94 and 115.77 K. The results have been used to estimate the excess Gibbs energy GE at these temperatures. The volume of mixing PE has been determined at 103.94 K and is found to be small and negative. In a comparison with the values of GE obtained by other authors, an attempt was made to estimate the value of HE, the molar enthalpy of mixing. The results are interpreted in the light of some simple theories of mixtures, suggesting that this is a case where the Lorentz rule of combination of collision diameters is valid.Item Thermodynamics of Binary Liquid Mixtures Involving Hydrogen Bromide, Hydrogen Chloride and Xenon(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (04), 1978) Calado, Jorge C. G.; Gray, Christopher G.; Gubbins, Keith E.; Palavra, Antonio M. F.; Soares, Virgilio A. M.; Staveley, Lionel A. K.; Twu, Chorng-HorngThe total vapour pressure of the systems hydrogen bromide+xenon and hydrogen bromide + hydrogcn chloride have been measured as a function of composition at 195.42 K. The results have been used to estimate the excess Gibbs function GE. The volume of mixing J/E has been determined for each system at 195.42 K. The HBr + Xe system departs considerably from ideal behaviour, while HBr+HCl is only slightly nonideal. Neither system exhibits an azeotrope at the temperature studied. These results, together with similar data reported previously for the HCl + Xe system (J.C.S. Faraday I, 1975, 71, 1372), are compared with theoretical calculations based on perturbation theory for liquids of nonspherical molecules. Agreement is good for all three systems. The results show that both dipolar and quadrupolar forces for the 1-IC1 and HBr molecules have a large eifect on the phase diagram, while other types of anisotropic intermolecular forces (overlap, dispersion, induction) appear to have a considerably smaller effect.Item Thermodynamics and constitution of silicate melts. The system PbO + PbF2+ SiO2(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Caley, William F.; Masson, Charles R.Activities of PbF2 in PbO + PbF2 and PbO + PbF2+ SiO2 melts with up to 40 mol% PbF2 were determined at 1073–1173 K by means of an electrochemical cell with CaF2 as solid electrolyte. The results, together with previous measurements of the activity of PbO, were interpreted in terms of a theory in which the anionic constitution of the melts is represented by O2–, F– and an equilibrium array of silicate and fluorosilicate ions of formula SinO3n+1–mF(2n+2–m)–m. The equilibrium constant k′ for the formation of fluorosilicate ions by the reaction F–+ SinO3n+1–mF(2n+2–m)–m= SinO3n–mF(2n+1–m)–m+1+ O2– was estimated to be 0.4 ± 0.025. This allowed the anionic distribution to be evaluated for basic melts. In addition to O2– and F–, the main anionic constituents in melts with XPbO/XSiO2 > 2.5 and XPbF2⩽ 0.25 are SiO4–4, SiO3F3–, SiO2F2–2, SiO3F–, Si2O6–7 and Si2O6F5–, with decreasing amounts of more highly fluorinated species. The volatile constituent SiF4 is also present in small amount and becomes increasingly significant as XSiO2/XPbO is increased. Substitution of PbO by PbF2 causes a net decrease in the mean chain length of the anions.Item Thermodynamics of Hydrobromic Acid in Dioxan+Water Mixtures from Electromotive Force Measurements at Different Temperatures(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (01), 1978) Das, Bijoy K. D; Das, Prasanna K.Electromotive force measurements of the cell Pt, H2/HBr(z>i), dioxan(A3 H2O(y)/AgBr/Ag have been made at 15, 25, 35 and 45“C for solvent compositions X = 10, 20, 30, 40, 60 %(w/w) of dioxan. These have been used to evaluate the standard potentials of the cell, the mean activity coefficient of HBr (molal scale) and the thermodynamic functions (mole-fraction scale) for the transfer of HBr from water to the respective dioxan+water media. The AG’ (free energy of transfer of the acid from water to various solvents) values along with those for hydrochloric acid, are briefly discussed in relation to ion solvation.Item Thermodynamics of the Liquid System Methane+Propane(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (08), 1974) Calado, Jorge C. G.; Garcia, Gerald A.; Staveley, Lionel A. K.The total vapour pressure of liquid mixtures of methane and propane has been measured as a function of composition at temperatures of 115.77 and 134.83 K. The activity coefficient of methane f\ and the excess Gibbs function of mixing GB have been evaluated from the vapour pressure measure ments, and the heat of mixing and the excess entropy of mixing SE have been estimated from the temperature dependence of GE and compared with direct calorimetric values. Values of the excess thermodynamic functions have been calculated from a simplified version of the Flory theory of mixtures, with allowance for departures from the geometric mean (Berthelot) combining rule. Calculations show that these deviations are very small, but not negligible.Item Thermodynamics of Adsorption Based on Gas-Solid Chromatography(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (3), 1978) Katsanos, Nicholas A; Lycourghiotis, Alexis; Tsiatsios, AthanasiosThe net retention volume in gas-solid chromatography is expressed in terms of changes in the thermodynamic functions of adsorption and then is used for the experimental determination of these functions. The differential entropy of adsorption is a linear function of the dilferential enthalpy of adsorption, accounted for by assuming a heterogeneous surface and an exponential distribution of adsorption sites with respect to the energy. A criterion for predicting the above “ thermodynamic compensation effect ” is derived. The net retention volume is also expressed in terms of molecular properties and its dependence on the number of carbon atoms in the molecule is explained. Finally, from the results of adsorption of alkanes and cycloalkanes on aluminium oxide, the frequency of the vibrations of the adsorbate molecules normal to the surface is calculated.Item Thermodynamics of Miscible Liquid Mixtures of Carbon Tetrachloride, n-Octanol and Water at 20°C(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (2), 1977) Platford, Robert F.Isopiestic measurements, using two independent sets of standards, have been combined with literature partition coefficient datajand have been used to calculate the activity coefficients of both components in the carbon tetrachloride + octanol system at 20'C. The presence of water in the system did not change the behaviour measured and it was concluded that partition coefficients can provide a reliable check on activity data, and vice versa.Item Thermodynamics of solution of two forms of DL-α-amino-n-butyric acid in water(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (1), 1977) Abraham, Michael H.; Ah-Sing, Eric; Marks, Robert E.; Schulz, Ronald A.Two crystalline polymorphic forms of DL-α-amino-n-butyric acid have been obtained and have been shown to be identical to the A-form and B-form previously described by Iitaka and coworkers. The two forms differ in heat of solution and in their solubility in water. We find that for the A-form at 298 K, ΔH°s= 374 cal mol–1, ΔG°s= 1772 cal mol–1 and ΔS°s=–4.7 cal K–1 mol–1 and for the B-form ΔH°s= 1653 cal mol–1, ΔG°s= 1883 cal mol–1 and ΔS°s=–0.8 cal K–1 mol–1. Although the B-form is the stable form at 298 K, it is predicted from the above measurements that the A-form should be the stable form above ∼ 326 K.Item Thermodynamics of n-Alkane+Dimethylsiloxane Mixtures: Part 3.—Excess Volumes(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (12), 1974) Dickinson, Eric; McLure, Tan A.Excess volumes have been measured dilatometrically for binary mixtures of six n-alkancs (n- pentane, n-hexane, n-heptane, n-octane, n-dccane and n-tetradecanc) with four linear dimethylsiloxanes (dimer, trimer, tetramer and pentamer) at 303.2 K, and for four other mixtures. The sign and magnitude of the excess volumes depend intimately upon the chain lengths of the oligomers. The phenomenological corresponding states theory of Patterson is shown to reproduce qualitatively the experimental chain length dependence. Suggestions for the success of the model arc discussed briefly in terms of the properties of the pure components, and the disadvantages of two other approaches —the van der,Waals one-fluid model and the Prigogine cell theory—are identified. An application of Bransted’s principle of congruence to ternary mixtures is discussed.Item Thermodynamics of n-Alkane+Dirnethylsiloxane Mixtures: Part 2.—Vapour Pressures and Enthalpies of Mixing(Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (12), 1974) Dickinson, Eric; McLure, Ian A.; Powell, Bernard H.The total vapour pressures of mixtures of n-hexane and hexamethyldisiloxane have been measured by a static equilibrium method at 303.15, 309.15 and 315.15 K. At each temperature the derived equimolar excess Gibbs free energy is small and positive. The excess enthalpy at 298.15 K, as determined by direct calorimetry, has a skew-parabolic composition dependence and a positive equimolar value of 126 ± 2 J mol–1. Theoretical excess functions for n-hexane + hexamethyldisiloxane are calculated from a one-fluid van der Waals model in conjunction with an experimental pure liquid reference substance; they agree well with experiment.